An approach to the calculation of multilayer magnetic shielding using artificial neural network

The electromagnetic interference has many undesired effects to the office equipments and the performance of technological devices. Therefore, electrical devices should have field protection mechanism against magnetic fields. The shielding mechanism prevents external magnetic field emitted from the device to the vicinity area. This work attempts to apply artificial neural network in order to estimate shielded magnetic field for multilayer shielding application. The multilayer magnetic shielding performances of cylindrical shaped ferromagnetic shields under extremely low frequency are investigated. For this purpose, three different ferromagnetic materials in cylindrical shape are chosen for magnetic shielding. The shielding performances of these materials are measured and a selected set of data is used to train and test an artificial neural network. The proposed neural network model achieves an intelligent decision for the shielded magnetic field level based on distance, unshielded magnetic field value, number of shield layer and skin-depth of the shield.     

Impact of chronic fluorosis on left ventricular diastolic and global functions

Sixty three patients with endemic fluorosis (36 males/27 females; mean age 33.9 ± 8.6 years) and 45 age, sex and body mass index (BMI) matched healthy controls (30 males/15 females; mean age 32.7 ± 8.8 years) were included in this study. Basic echocardiographic measurements, left ventricular diastolic parameters and left ventricular myocardial performance index (MPI) were measured. The left ventricular MPI was calculated as (isovolumic contraction time + isovolumic relaxation time) / aortic ejection time by Doppler. The urine fluoride levels of fluorosis patients were significantly higher than control subjects as expected (1.9 ± 0.1 mg/l vs 0.4 ± 0.1 mg/l respectively; P < 0.001). Isovolumic relaxation time (IVRT) and deceleration time (DT) were significantly higher in fluorosis patients than in controls (for IVRT 106.9 ± 15.6 ms vs 96.7 ± 12.2 ms; P < 0.001 and for DT 211.7 ± 30.7 ms vs 188.0 ± 30.0 ms; P < 0.001, respectively). MPI was significantly higher in fluorosis patients than in controls (0.62 ± 0.15 ms vs 0.49 ± 0.10 ms; P < 0.001, respectively). We have shown that chronic fluorosis patients had left ventricular diastolic and global dysfunctions.     

3D Printing of Polyvinylidene Fluoride Based Piezoelectric Nanocomposites: An Overview

Recently, polyvinylidene fluoride (PVDF) based nanocomposites have attracted much attention for next-generation wearable applications such as promising piezoelectric energy harvesters (nanogenerators), energy storage devices, sensing devices, and biomedical devices due to their high flexibility, and high dielectric and piezoelectric properties. 3D printing technology, PVDF based piezoelectric nanocomposites, the studies based on 3D printing of PVDF based piezoelectric nanocomposites by inkjet printing and fused deposition modeling, and enhancements of energy harvesting and storage performance of nanocomposites by structural design are comprehensively overviewed here. An insight is provided into 3D printing techniques, structure and properties of PVDF based polymers, various nanofillers and production methods for nanocomposites, solutions to enhance β phase (crystallinity) of PVDF, and improvements of nanocomposites’ breakdown strength, discharged energy density, and piezoelectric power output by mentoring structural design.     

In vacuo production of α-AlB12, C4AlB24, AlB12C2 and Al3B48C2 powders

The production of pure powder samples of boron-rich ternary Al–B–C phases was investigated in vacuum at temperatures between 1400 °C and 1600 °C, using a range of different starting powders. Compacted powder mixes of B–AlB₂–B₄C, Al–B–C, Al–B–B₄C, B–C–AlB₂, B–AlB₂ and Al–B were heated for 1–2 h under vacuum in a carbon resistance furnace and the products characterised by X-ray diffraction. It was found impossible to produce significant quantities of C₄AlB₂₄ under these conditions, but >95% pure samples of α-AlB₁₂, AlB₁₂C₂ and Al₃B₄₈C₂ were obtained. This study is a precursor to further research aimed at producing dense B₄C-type materials which might offer the advantages of easier densification and fabrication as compared with B₄C itself.     

Susceptor-assisted fast microwave sintering of TiN reinforced SiAlON composites in a single mode cavity

In the present study, 17 wt % TiN reinforced α-β SiAlON composites were sintered at low temperature by susceptor-assisted microwave heating. The effect of TiN addition on dielectrical properties of starting powders, as well as the influence of sintering temperature on phase evolution, microstructure development and mechanical properties of α/β-SiAlON-TiN composites were investigated. The obtained results showed that TiN addition increased the microwave absorbing properties which is reflected in the peak sintering temperature. Thus, the α:β ratio decreased and mechanical properties were improved, especially the fracture toughness of the composites. Furthermore, an estimate of energy consumption during microwave assisted sintering at the laboratory scale is presented. As a result, the highest values for relative density (97.1%), Vickers hardness (13.35 ± 0.47 GPa), and fracture toughness (7.52 ± 0.54 MPa m^1/2) were obtained by microwave sintering for 30 min at 1300 °C.     

Influence of Laser Peening With and Without Coating on the Surface Properties and Stress Corrosion Cracking Behavior of Laser-Welded 304 Stainless Steel

Metallurgical and Materials Transactions A - This study aims to investigate the effect of laser peening with (LP) and without coating (LPwC) process on subsurface microstructural evolution,...     

TATB thermal decomposition: An improved kinetic model for explosive safety analysis

We investigate and model the cook-off behavior of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) to understand the response of explosive systems in abnormal thermal environments. Decomposition has been explored via conventional ODTX (one-dimensional time-to-explosion), PODTX (ODTX with pressure-measurement), PyGC-MS (pyrolysis gas chromatography mass spectrometry), TGA (thermo-gravimetric analysis), DSC (differential scanning calorimetry), and IR (infrared spectroscopy) experiments under isothermal and ramped temperature profiles. The data were used to fit rate parameters for proposed reaction schemes in a MATLAB thermo-chemical computational model. These parameterizations were carried out utilizing a genetic algorithm optimization method on LLNL's high-performance computing clusters, which enabled significant parallelization. These results include a multi-step reaction decomposition model, identification of likely autocatalytic gas-phase species, accurate high-temperature sensitization, and prediction of confined system pressurization. This model will be scalable to several applications involving TATB-based explosives, like LX-17, including thermal safety models of full-scale systems.     

Optimization of weld bead geometry of laser welded ANSI 304 austenitic stainless steel using grey-based Taguchi method

This paper investigates the quality characteristics of the welding geometry of the laser welding process for the ANSI 304 austenitic stainless steel, with the use of a pulsed Nd:YAG laser welding system. Laser welding of 2 mm thick ANSI 304 stainless steel is performed at three different levels of three factors, i. e., peak power, welding speed and pulse duration. In this study, a multi-response optimization problem is developed to achieve weld bead geometry with full penetration as well as a narrow bead width and minimum crater. Grey relational analysis based on Taguchi orthogonal array is used to present an effective approach for the optimization of laser welding process parameters. Regression equations between the welding parameters and the bead dimensions for laser welded austenitic stainless steels are developed, which are used in predicting the penetration, width and crater. Finally, the equations are tested for values different from the levels of the parameters in the orthogonal array. It will be beneficial to engineers for continuous improvement in laser welded product quality.     

TATB thermal decomposition: Expanding the molecular profile with cryo-focused pyrolysis GC-MS

Understanding the molecular composition of high explosives during thermal decomposition is vital for predicting the sensitivity, safety, and performance of explosive materials. The thermal decomposition of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) has been linked to the formation of furazans through a series of dehydration reactions of the NO₂ and NH₂ groups on the phenyl ring, along with breakdown into small molecules (≤120 amu). Molecular identification of compounds formed in this transformation of the furazans to light gases has been lacking. To address this, we have applied a pseudo-confined sampling system in a cryo-focused pyrolysis gas chromatography-mass spectrometry (pyGC-MS) system to molecularly identify these intermediates. By design, sublimation of TATB, which has complicated MS analyses of thermal degradation, was significantly reduced and additional compounds were identified with potential structural information. In addition to the known furazan compounds, one of these compounds forms from the loss of oxygen from benzo-trifurazan (F₃) and produces an open ring structure that may be the first step in the formation of lower molecular weight furazan breakdown products. The loss of a nitro group from benzo-monofurazan (F₁) was also discovered and implicates the formation of oxidizing NO₂ gas in the thermal decomposition mechanism. These findings are vital for understanding the proper heat flow from energetic materials on a molecular level, necessary when measuring enthalpy and developing decomposition models based on kinetic parameters.     

Prevalence of juvenile chronic arthritis and familial Mediterranean fever in Turkey: a field study

OBJECTIVE: To investigate the prevalence of juvenile chronic arthritis (JCA), familial Mediterranean fever (FMF), and Beh?et's disease in Turkish children through a field survey. METHODS: The field survey was based on cluster centering with 2 level strata. A total of 46,813 children were screened. For the diagnosis of chronic arthritis and Beh?et's previously suggested criteria were used. We have developed criteria for the diagnosis of probable FMF. Children previously diagnosed to have these diseases were also defined and included. RESULTS: JCA was found in 6.4/10,000. 2.8/10,000 children were previously diagnosed as FMF (minimum phenotype frequency). Together with the probable diagnosis of FMF, the prevalence increased to 9.3/10,000. The findings were also compared with those of our center. None of the 46,813 children had Beh?et's disease. CONCLUSION: The prevalence of chronic arthritis is similar to the other childhood populations reported. However, FMF has a very high prevalence.